The present invention relates to magnetic disk storage systems. In particular, the present invention relates to an air bearing slider for carrying a magnetic read/write head in a magnetic storage system.
Magnetic storage systems are used for magnetically storing information and are typically used for long term storage in a computer system. A magnetic head assembly which includes a magnetic head and a slider moves relative to a surface of a magnetic disk.
Magnetic head assemblies or sliders that fly relative to a rotating magnetic disk have been used extensively. Typically, these assemblies comprise a slider which carries a magnetic transducer. It is desirable to have the magnetic transducer "fly" as close to the disk surface as possible, and have the flying height be uniform regardless of variable flying conditions, such as speed variation from inside track to outside track and skew caused by rotary actuators.
During operation of a magnetic disk storage system, the magnetic head carried on a slider repeatedly "lands" and "takes-off" from the surface of the magnetic disk. Over the life of the magnetic storage system, these landings and take-offs are the source of the majority of head and slider wear. Each take off and landing is a relatively stressful operation in which the slider/head assembly is dragged along the surface of the magnetic disk. This dragging action gradually wears away the slider and magnetic head.
Each time the slider is started and stopped, minute amounts of material build up upon the slider surface. This increases the coefficient of friction of the slider surface. As the number of times the slider has been stopped and started increases, the coefficient of friction between the slider and the disk surface correspondingly increases. This is due to a build up of small particles along the surface of the slider.
A contact start/stop test is a test used in magnetic disk drive systems to determine the coefficient of friction between the slider surface and the surface of the magnetic storage disk. The contact start/stop test is also used to measure break-away torque. Breakaway torque is the torque required to begin the rotation of the magnetic disk from a stopped condition. If the break-away torque is too high, the disk cannot be rotated. Typically, the slider/disk surface interface must be below a predetermined maximum coefficient of friction level and the break-away torque must be below a maximum for that particular disk to qualify for use.
The magnetic disk surface/slider interface is qualified using a contact start/stop standard test that ranges from 20,000 to 40,000 cycles. For these tests, the coefficient of friction and the breakaway torque must be below predetermined maximum levels after a predetermined number of take-off and landing cycles. Break-away torque is measured in ounces-inches and relates to the torque at which the slider breaks away from the surface of the magnetic disk so that the disk can rotate and the slider can begin to fly. A contact start/stop standard test requires a maximum break-away torque to be less than a specified value, determined by the number of head/disk interfaces, the landing zone radius, and minimum available motor torque.
As the magnetic disk storage system is used, the break-away torque and coefficient of friction increase due to particle build up on the slider surface. This eventually leads to a system failure at which time the magnetic head and disk require replacement. As evident from this discussion, a slider in a magnetic disk storage system which reduces frictional build up of particles along the surface of the slider, and therefore reduces the rate at which the break-away torque and the coefficient of friction increase over time due to repeated take-offs and landings, would be a significant contribution to the art.